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      <title>Zookeeper是如何处理节点故障的？ - 交互式测验</title>
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      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>Zookeeper是如何处理节点故障的？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
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                <div class="quiz-body">
                    <div class="progress-bar">
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      <script>
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  {
    "question": "在Zookeeper集群中，当检测到现任Leader节点发生故障后，会立即触发什么核心流程？",
    "options": [
      "集群进入只读模式，等待管理员手动恢复。",
      "所有节点立即停止服务，直到故障节点恢复。",
      "触发新的Leader选举机制，以选举出新的Leader。",
      "客户端会自动连接到数据最新的Follower节点。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "根据文档描述，一旦检测到Leader节点失效，集群中的其他节点（Follower和Observer）会立即进入选举状态，启动Leader选举流程，以保证集群能够尽快恢复服务。",
    "source": "文档中「2. 选举机制」-「选举准备」部分",
    "hint": "文档中提到：“当检测到 Leader 节点失效时，集群中的所有 Follower 和 Observer 节点会进入选举状态...”"
  },
  {
    "question": "Zookeeper使用心跳机制（Heartbeat）的主要目的是什么？",
    "options": [
      "检测节点是否存活，作为故障判断的依据。",
      "同步各个节点之间的系统时间。",
      "在节点间广播事务日志。",
      "统计客户端的活跃连接数。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "心跳机制是Zookeeper进行故障检测的基础。每个节点会定期向其他节点发送心跳信号，如果一个节点在规定时间内没有收到另一个节点的心跳，就会认为该节点可能已经发生故障。",
    "source": "文档中「1. 故障检测」-「心跳机制」部分",
    "hint": "思考一下，在分布式系统中，最直接判断一个远程服务是否“在线”的方法是什么？文档中提到了“Ping”。"
  },
  {
    "question": "在Zookeeper的Leader选举投票过程中，一个节点需要满足什么关键条件才能成功当选为新的Leader？",
    "options": [
      "该节点必须拥有集群中最大的服务器ID。",
      "该节点必须是第一个发起投票的节点。",
      "该节点的投票需要获得超过半数节点的支持。",
      "该节点必须拥有最完整的事务日志，无论获得多少票。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "Zookeeper的选举完成依赖于ZAB协议，其中一个核心原则是，一个候选节点必须获得超过半数（Quorum）的选票才能成为新的Leader。这确保了选举出的大多数节点都认可的领导者，从而维护了集群的一致性。",
    "source": "文档中「2. 选举机制」-「选举完成」部分",
    "hint": "在分布式共识算法中，“少数服从多数”是一个常见原则。文档中提到了一个具体的比例要求。"
  },
  {
    "question": "Zookeeper的Quorum机制（超过半数节点确认）主要为哪一类操作提供强一致性保障？",
    "options": [
      "客户端的会话连接请求。",
      "集群的Leader选举过程。",
      "数据的写操作。",
      "数据的读操作。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确指出，Zookeeper的写操作需要得到超过半数（Quorum）节点的确认后才算成功。这个机制确保了即使有少数节点发生故障，已经提交的数据也不会丢失，从而保证了数据的一致性和持久性。",
    "source": "文档中「4. 分布式一致性保障」-「Quorum 机制」部分",
    "hint": "为了保证数据不会因为部分节点故障而丢失，哪种操作最需要“大多数”节点的确认？"
  },
  {
    "question": "在新Leader选举成功后，进行数据恢复时，数据快照（Snapshot）扮演了什么重要角色？",
    "options": [
      "完全替代事务日志，成为唯一的数据恢复来源。",
      "用于验证其他Follower节点数据的有效性。",
      "作为恢复的基准点，以加速恢复过程，减少需要重放的事务日志数量。",
      "仅用于记录集群的配置信息，与业务数据无关。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "数据快照是某个时间点全量数据的备份。在恢复时，新的Leader会首先加载最新的快照，将内存状态快速恢复到某个较近的时间点，然后再应用该时间点之后的所有事务日志。这比从头开始重放所有日志要快得多，因此其主要作用是“减少恢复时间”。",
    "source": "文档中「3. 数据恢复」-「数据快照」部分",
    "hint": "如果事务日志非常多，从头开始一条条执行会很慢。有没有一种方法可以“走捷径”？"
  },
  {
    "question": "ZAB协议（Zookeeper Atomic Broadcast）在Zookeeper的故障处理和数据一致性中起到了什么核心作用？",
    "options": [
      "它是一种专门用于压缩数据快照的算法。",
      "它定义了客户端与服务器之间的通信加密标准。",
      "它是一种仅用于在选举阶段进行投票的临时协议。",
      "它确保了写操作在集群中被一致地广播和应用，并保证了Leader故障切换后的一致性。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "ZAB协议是Zookeeper实现分布式一致性的基石。它不仅规范了Leader选举的过程，更重要的是，它定义了一套原子广播协议，确保所有写请求（事务）都能以一个全局一致的顺序被应用到所有节点上，即使在发生Leader切换的情况下也能维持这种一致性。",
    "source": "文档中「4. 分布式一致性保障」-「ZAB 协议」部分",
    "hint": "这个协议的名称中包含了“Atomic Broadcast”（原子广播），这暗示了它的主要功能与数据分发和顺序有关。"
  },
  {
    "question": "根据文档，一个新当选的Leader节点在恢复数据时，正确的步骤顺序是什么？",
    "options": [
      "首先加载最新的数据快照，然后应用该快照之后的所有事务日志。",
      "仅重放所有的事务日志，不使用数据快照。",
      "向所有Follower节点请求数据，并选择最完整的一份进行复制。",
      "仅加载最新的数据快照，并丢弃所有未应用的事务日志。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "为了兼顾恢复速度和数据完整性，Zookeeper的恢复策略是两步走：首先，通过加载最新的快照文件，快速将内存数据恢复到一个比较新的状态；然后，再应用快照生成之后到当前时间点的所有事务日志，以确保数据恢复到最新的、完全一致的状态。",
    "source": "文档中「3. 数据恢复」-「数据快照」部分",
    "hint": "文档中描述了一个“先...然后...”的恢复流程，结合了快照和日志的优点。"
  }
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                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  